1. Field of the Invention
The invention relates to an article of footwear, such as a shoe, particularly a sports shoe, and more particularly a shoe adapted for running, race walking, or other athletic activities.
Articles of footwear of the aforementioned type can be used in fields such as walking or flat or mountain racing, hiking, or snowboarding, skiing, snowshoeing, roller skating, skateboarding, cycling, ball-playing sports, or the like.
2. Description of Background and Relevant Information
An article of footwear can have a low upper or a high upper. Footwear can also be relatively flexible or, on the contrary, they can be more rigid. However, the wearer's foot, in any case, must be adequately held. Indeed, an adequate support of the foot in the upper allows the article of footwear to be put to its best use.
With a flexible low shoe, such as used for mountain running, for example, adequate support facilitates the rolling movement of the foot as well as the transmission of sensory information. In particular, a device for tightening the upper is adapted to hold at least the wearer's instep in the area of the vamp.
Traditionally, a tightening device includes a lace, on the one hand, and points for connecting the lace to the upper, on the other hand. These connecting points are defined by keepers or guides associated with lateral and medial quarters of the upper. The lace follows a path that leads it alternately from one quarter to the other. It thus suffices to pull on the lace to bring the quarters closer together and to tighten the upper. Next, the blocking of the lace maintains the lace in its tightened position. A first problem to be resolved by a good tightening device lies in adapting to various foot morphologies and in achieving comfort, that is, support without excessive pressure. Another problem involves maintaining the tightening comfort during use of the shoe, i.e., during walking or running.
In the static position, indeed, traction on the lace substantially tensions the lace in the area of the instep or in the area of the flexion crease, such as the flexion crease between the instep and the lower leg. There is, however, less tension toward the toes. Therefore, the tightening is generally more substantial toward the instep or the flexion crease than toward the toes. Thereafter, when walking or while engaging in a sporting activity, the deformations of the upper enable a balancing of the tensions along the lace. As a result, tightening is better distributed. However, it has been observed that the foot is not always properly supported, in the sense that this support is not sufficiently uniform along the shoe.
Certain portions of the foot are overly tightened while others are not sufficiently tightened; or a given portion of the foot is sometimes too tight, sometimes not tight enough.
In fact, during a walking cycle, the shape of the foot changes rapidly. Some portions alternately bend and straighten out. Sections of the foot may broaden out, and then narrow down, or they may thicken, and then thin down. The walking cycle is so fast that there is not enough time for the tensions in the lacing to balance completely. Thus, disparities remain in the distribution of the tightening of the upper of the shoe. Consequently, the foot is generally not completely held during use, since the tightening disparities reverberate on the foot.